FIGURE 99.5 Cor pulmonale secondary to upper airway obstruction A: This is a 2-year-old boy with tachypnea and dyspnea The chest film shows a large heart and mild interstitial edema B: The lateral view of the neck shows obstructing enlarged adenoids and tonsils C: The chest film days after adenoidectomy shows a decreased heart size and improvement in interstitial edema For children with underlying conditions, it is important to understand the status of their disease and any recent changes in therapy The possibility of acute intercurrent illness or insult should also be considered CXRs are often diagnostic, although findings may lag behind the acute clinical process Lymphatic and interstitial fluid accumulations may be visible as Kerley A and B lines (septal lines; Fig 99.6 ), which represent interstitial edema, tangential to the radiograph beam The B lines, which lie in the periphery, are often the first findings Unlike blood vessels, these radiopacities will reach the lung edge As edema progresses, Kerley A lines near the hilum may occur, and ultimately, a butterfly pattern with a central predominance of shadows can be seen Although these findings are not specific, transient changes in an appropriate clinical context usually signify edema Bedside ultrasound can also be very